On January 20, 2022 the Society for the Study of Addiction published a systematic meta-review of meta-analyses on residual neurocognitive effects of cannabis use. In plain language, this publication was a review of many other reviews that each looked at a number of studies regarding how marijuana effects people’s ability to think. The reviews included a total of more than 43,000 subjects (individuals who used marijuana/cannabis) and examined multiple domains of cognitive functioning including:

• Executive functions
  • Decision-making
  • Response inhibition
  • Flexibility
  • Working memory
• Learning and memory
  • Visual learning
  • Visual memory
  • Verbal learning
  • Verbal memory
  • Prospective memory
• Complex attention
• Processing speed
• Perceptual motor function
• Language

The study’s co-author, Dr. Alexandre Dumais – Associate Clinical Professor of Psychiatry at Université de Montréal, was quoted by Neuroscience News saying, “Our study enabled us to highlight several areas of cognition impaired by cannabis use, including problems concentrating and difficulties remembering and learning, which may have considerable impact on users’ daily lives.”

In general, the most pronounced effects were in participants’ abilities with regard to verbal memory and verbal learning. Verbal memory is a form of short-term memory specifically for verbally presented information. Degraded verbal memory and learning have the ability to impact almost any individual’s life, but this is especially true for adolescents who are still in school.

Many of the cognitive effects of marijuana use found in this study seem to be magnified in chronic (heavy) marijuana users and in individuals who start using marijuana during adolescence. Dr. Dumais commented on the implications of the research on adolescent academic performance saying, “Cannabis use in youth may consequently lead to reduced educational attainment, and, in adults, to poor work performance and dangerous driving. These consequences may be worse in regular and heavy users.”